Semiconductor lasers are well-known in the art and are described in the following references, the disclosures of which are incorporated herein by reference:
1. P. T. Ho, L. A. Glasser, E. P. Ippen, and H. A. Haus, "Picosecond Pulse generation with a CW (GaAl)As Laser Diode," Appl. Phys. Lett., V. 33, p. 241-243, Aug. 1978.
2. L. A. Glasser, "C. W. Mode Locking of a GaInAsP Diode Laser," Elect. Lett., V. 14, p. 725-726, November 1978.
3. P. T. Ho, "Coherent Pulse Generation with a GaAlAs Laser by Active Mode Locking," Elect. Lett., V. 15, p. 527-28, August 1979.
4. E. P. Ippen, D. J. Eilenberger, and R. W. Dixon, "Picosecond Pulse Generation by Passive Mode-Locking of Diode Lasers," Appl. Phys. Lett., V. 37, p. 267-270, August (1980).
5. M. B. Holbrook, W. E. Sleat, and D. J. Bradley, "Bandwidth-Limited Picosecond Pulse Generation in an Actively-Mode Locked GaAlAs Diode Laser," Appl. Phys. Lett., V. 37, p. 59-61, July 1980.
6. J. P. Van der Ziel and R. M. Mikulyak, "Mode-locking of Strip Buried Heterostructure (AlGa)As Lasers using an External Cavity," J. Appl. Phys., V. 51, p. 3033-3037, June 1980.
7. H. Ito, H. Yokoyama and H. Inaba, "Bandwidth Limited Picosecond Optical Pulse Generation from Actively Mode Locked AlGaAs Diode Laser," Elect. Lett., V. 16, p. 620-621, July 1980.
8. A. Yariv, "Internal Modulation in Multimode Laser Oscillators," J. Appl. Phys. V. 36, p. 388, 1965.
9. R. W. Dixon and W. B. Joyce, "A Possible Model for Sustained Oscillations (Pulsations) in (AlGa)As Double-Heterostructure Lasers," IEEE J. Quart. Elect., V. QE-15, pp. 470-474, June 1979.
10. A. E. Diemes, E. P. Ippen and C. V. Shank, Appl. Phys. Lett. 19, p. 258 (1971).
Briefly, a typical gallium arsenide (GaAs) semiconductor laser requires three semiconductive layers, including a p-type gallium arsenide layer sandwiched between p-type and n-type gallium-aluminum-arsenide semiconductor layers which, under the influence of an external electric field, inject holes and electrons, respectively, into the sandwiched layer. The external electric field is applied by an electric field-applying electrode disposed on top of the three layers. Each hole and electron pair meeting in the sandwiched layer recombines and creates a photon, the photons so created then resonating in the sandwiched layer so as to produce a laser beam. The sandwiched semiconductor layer thus functions as a laser cavity.
Self-pulsing GaAs semiconductor lasers are useful as high frequency signal generators because their laser output beam is pulsed rather than a continuous wave. The problem in this art has been to reliably reproduce devices having a very high pulse repetition rate with extremely good temporal stability. Currently available devices often suffer from the disadvantage that their pulse rate varies significantly during the life of the device.
A practical problem exists because manufacturers of such devices cannot reliably reproduce a self-pulsing laser of a particular repetition rate. Typically, a manufacturer must operate each device after it is manufactured in order to empirically determine whether it is self-pulsing and, if it is self-pulsing, what its repetition rate is.